a-Axis GaN/AlN/AlGaN Core–Shell Heterojunction Microwires as Normally Off High Electron Mobility Transistors

Micro/nanowire-based devices have been envisioned as a promising new route towards improved electronics and opto-electronics applications, which attracts considerable research interests. However, suffering from applicable strategies to synthesize uniform core-shell structures to meet the requirement for the investigations of electrical transport behaviors along length direction or HEMT devices, heterojunction wire-based electronics have been explored limitedly. In the present work, GaN/AlN/AlGaN core-shell heterojunction microwires on patterned Si substrates were synthesized without any catalyst via MOCVD. The as-synthesized microwires had low dislocation, sharp and uniform heterojunction interfaces. Electrical transport performances were evaluated by fabricating HEMTs on the heterojunction microwire channels. Results demonstrated that normally-off operation was achieved with a threshold voltage of 1.4 V, a high on/off current ratio of 108, a transconductance of 165 mS/mm and a low subthreshold swing of 8...